| ( | 3 | + | X | ) | ( | 4 | + | X | ) | ( | 5 | + | X | ) | = | 120 |
| Left side of the equation = | 3 | ( | 4 | + | X | ) | ( | 5 | + | X | ) | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 3 | × | 4 | ( | 5 | + | X | ) | + | 3 | X | ( | 5 | + | X | ) | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 12 | ( | 5 | + | X | ) | + | 3 | X | ( | 5 | + | X | ) | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 12 | × | 5 | + | 12 | X | + | 3 | X | ( | 5 | + | X | ) | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 60 | + | 12 | X | + | 3 | X | ( | 5 | + | X | ) | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 60 | + | 12 | X | + | 3 | X | × | 5 | + | 3 | X | X | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 60 | + | 12 | X | + | 15 | X | + | 3 | X | X | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 60 | + | 27 | X | + | 3 | X | X | + | X | ( | 4 | + | X | ) | ( | 5 | + | X | ) |
| = | 60 | + | 27 | X | + | 3 | X | X | + | X | × | 4 | ( | 5 | + | X | ) | + | X | X | ( | 5 | + | X | ) |
| = | 60 | + | 27 | X | + | 3 | X | X | + | X | × | 4 | × | 5 | + | X | × | 4 | X |
| = | 60 | + | 27 | X | + | 3 | X | X | + | X | × | 20 | + | X | × | 4 | X | + | X |
| = | 60 | + | 47 | X | + | 3 | X | X | + | X | × | 4 | X | + | X | X | ( | 5 | + | X | ) |
| = | 60 | + | 47 | X | + | 3 | X | X | + | X | × | 4 | X | + | X | X | × | 5 |
| 60 | + | 47 | X | + | 3 | X | X | + | X | × | 4 | X | + | X | X | × | 5 | = | 120 |